Cypress CY25822-2 User Manual
Page 2
CY25822-2
Document #: 38-07531 Rev. **
Page 2 of 9
Serial Data Interface
To enhance the flexibility and function of the clock synthesizer,
a two-signal serial interface is provided. Through the Serial
Data Interface, various device functions such as individual
clock output buffers, etc., can be individually enabled or
disabled.
The registers associated with the Serial Data Interface
initializes to their default setting upon power-up, and therefore
use of this interface is optional. Clock device register changes
are normally made upon system initialization, if any are
required. The interface can also be used during system
operation for power management functions.
Data Protocol
The clock driver serial protocol accepts byte write, byte read,
block write, and block read operation from the controller. For
block write/read operation, the bytes must be accessed in
sequential order from lowest to highest byte (most significant
bit first) with the ability to stop after any complete byte has
been transferred. For byte write and byte read operations, the
system controller can access individual indexed bytes. The
offset of the indexed byte is encoded in the command code, as
described in Table 1.
The block write and block read protocol is outlined in Table 2
while Table 3 outlines the corresponding byte write and byte
read protocol.The slave receiver address is 11010100 (D4h).
Pin Description
Pin No.
Pin Name
Pin Type
Pin Description
1
CLKIN
Input
48-MHz or 66-MHz Clock Input.
2
VDD
Power
Power Supply for PLL and Outputs.
3
GND
Ground
Ground for Outputs.
4
CLKOUT
Output
48-MHz or 66-MHz Spread Spectrum Clock Output.
5
REFOUT
Output
Non-spread Spectrum Reference Clock Output.
6
SDATA
I/O
I
2
C-compatible SDATA.
7
SCLOCK
Input
I
2
C-compatible SCLOCK.
8
PWRDWN#
Output
LVTTL Input for PowerDown# Active Low.
Table 1. Command Code Definition
Bit
Description
7
0 = Block read or block write operation
1 = Byte read or byte write operation
(6:0) Byte offset for byte read or byte write operation. For block read or block write operations, these bits should be ’0000000’
Table 2. Block Read and Block Write Protocol
Block Write Protocol
Block Read Protocol
Bit
Description
Bit
Description
1
Start
1
Start
2:8
Slave address – 7 bits
2:8
Slave address – 7 bits
9
Write = 0
9
Write = 0
10
Acknowledge from slave
10
Acknowledge from slave
11:18
Command Code – 8 bits
'00000000' stands for block operation
11:18
Command Code – 8 bits
'00000000' stands for block operation
19
Acknowledge from slave
19
Acknowledge from slave
20:27
Byte Count – 8 bits
20
Repeat start
28
Acknowledge from slave
21:27
Slave address – 7 bits
29:36
Data byte 1 – 8 bits
28
Read = 1
37
Acknowledge from slave
29
Acknowledge from slave
38:45
Data byte 2 – 8 bits
30:37
Byte count from slave – 8 bits
46
Acknowledge from slave
38
Acknowledge
....
......................
39:46
Data byte from slave – 8 bits
....
Data Byte (N–1) –8 bits
47
Acknowledge
....
Acknowledge from slave
48:55
Data byte from slave – 8 bits